is there anything one can put in front or at the back of a permanent magnet which can reduce or totally remove the magnetic force of the magnet
You can shock a magnet into loosing it's force. If you bang it - gently though so you don't break it.
in electromagnet you can, but in a permanent magnet I don't know of any way , I think hitting it into something hard can, but it could also destroy its magnetic field.
If you mean to reduce the power temporarily then any magnetic material will do the shielding. The magnetic field will flow through the material in preference to propagating through free space. On the other side of it the magnetic field is much reduced. The amount of the reduction depends on the size, quantity and magnetic properties of the shield chosen.
